1. Technical Field
The present invention relates to an electronic circuit substrate that can be used in a display panel or the like, and a production process thereof.
2. Background Art
Electroluminescence (EL) display apparatuses equipped with display panels composed of light-emitting devices utilizing the EL generated by a magnetic field as a result of the generation or transport of a charge in a substance, the guiding of light or the recombination of a charge, such as an organic EL device using an organic compound material, have recently attracted considerable attention. Organic EL devices consist of red EL devices having a structure that emits red light, green EL devices having a structure that emits green light, and blue EL devices having a structure that emits blue light. Color display apparatuses can be realized by combining these three red (R), green (G) and blue (B) organic EL devices into a single pixel emission unit, and arranging a plurality of these pixels on a panel in the form of a matrix. Known methods for driving display panels employing a color display apparatus consist of simple matrix driving and active matrix driving. Since EL display apparatuses of the active matrix driving type offer the advantages of lower power consumption and reduced crosstalk between pixels as compared with those of the simple matrix driving type, they are suitable for large-screen display apparatuses and high-definition display apparatuses in particular.
Anode power supply lines, cathode power supply lines, scan lines responsible for horizontal scanning and data lines arranged intersecting each scan line are formed in the form of a matrix in the display panels, namely the electronic circuit substrates, of active matrix driving types of EL display apparatuses. An RGB subpixel is formed at each RGB intersection of the scan lines and data lines.
Scan lines are connected to the gate of a field effect transistor (FET) for selecting scan lines for each subpixel, data lines are connected to the source thereof, and the gate of an FET for driving light emission is connected to the drain thereof. A drive voltage is applied to the source of the light emission driving FET via the anode power supply lines, and the anode terminal of the EL device is connected to the drain D thereof. A capacitor is connected between the gate and source of the light emission driving FET. Moreover, a ground potential is applied to the cathode terminal of the EL device via the cathode power supply lines.
In this manner, in order to actively drive an organic EL device, two or more thin film transistors (TFT) such as FETs are required for each subpixel of an electronic circuit substrate, and an organic EL device and a plurality of TFT devices are arranged within a single subpixel.
The TFT device may be an inorganic TFT device formed with an inorganic material such as polysilicon, or an organic TFT device formed with an organic material containing an organic semiconductor. In the case of an organic TFT device, various techniques have been proposed for the gate insulating film, such as a method in which an inorganic insulating film such as SiO2 is formed by vacuum deposition, and a method in which a organic insulating film such as polyaniline is formed by spin coating or printing.
There is also a method for forming a gate insulating film by anodic oxidation of the gate electrode for either type of TFT device (see Japanese Patent Application Laid-open No. 2004-235298). In the case of attempting to form an insulating film (such as a gate insulating film) on a metal pattern of an electrode or wiring within a display panel using this anodic oxidation method, since the portions where the insulating film is desired to be provided become completely electrically connected, it is necessary to carry out anodic oxidation by providing distribution patterns and applying a voltage from the outside to all patterns.
However, it is also necessary to cut away those distribution patterns that are no longer required at those portions covered by the formed insulating film.
Although examples of techniques for cutting away the distribution patterns following anodic oxidation include etching and laser irradiation and heating (see Japanese Patent Application Laid-open No. H5-343688), the production process is cumbersome and complex for each of these techniques.